My previous U.S. Pat. No. 5,422,043 disclosed an improvement in a sparger diffuser that efficiently distributes tiny gas bubbles into a liquid. It accomplishes this essentially with a gas-permeable diffuser having a high surface energy interface with the liquid allowing fine bubbles to depart from the interface surface and enter the liquid. The high surface energy interface is preferably backed up with a low surface energy material preventing liquid backflow and offering low resistance to gas through flow. For the details involved in accomplishing these effects with a thin and inexpensive diffuser, U.S. Pat. No. 5,422,043 is hereby incorporated by reference.
Scaling up a sparger so that its diffuser has a large surface area that can distribute fine bubbles throughout a large volume of liquid has required some other departures from the sparger art. It is desirable, for example, but difficult to ensure, that a sparger with a large area is not inflated and made buoyant during operation. If the diffuser of the sparger is made of two layers, which is often desirable, it is preferable that a satisfactory way be found for these to remain in contact with each other throughout the working area of the sparger. Billowing of the diffuser is to be avoided, as is anything that would make otherwise fine bubbles coalesce or merge into larger bubbles. Large spargers can also benefit from being made of flexible materials, so they are easy to handle. This invention addresses these and other problems to be solved in an efficient and low cost sparger having a large diffuser area.